1. Field of the Invention
Aspects of the invention relate to apparatus and methods to perform fast handovers. More particularly, aspects of the invention relate to an apparatus and a method to perform a fast handover that is capable of determining whether to switch an internet protocol (IP) using a received, unique code of an access router when a mobile node performs a fast handover in a wireless network.
2. Description of the Related Art
A rapid increase of users of mobile communication services has led to the activation of mobile communication services supporting multimedia communications, and seamless communication services have been requested by mobile users. Accordingly, it has become important to achieve a fast handover in the wireless local area network (LAN) environment based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard specification.
FIG. 1 illustrates a conventional wireless LAN environment. As illustrated, the wireless LAN environment includes a mobile node 1, a first access point 21, a second access point 22, a third access point 23, a fourth access point 24, a first access router 31 and a second access router 32. The conventional wireless LAN environment will be explained under the assumption that the mobile node connected to the first access point 21 passes through respective cells managed by the first access point 21, the second access point 22, the third access point 23, and the fourth access point 24 in sequence. The first to fourth access points 21, 22, 23 and 24 periodically transmit beacon signals to indicate their cells so that the mobile node 1 in motion can know with which access point it can attach to the wired network.
In the communications denoted by 211 in FIG. 1, the mobile node 1 receives a beacon signal from the first access point 21. Based on the received beacon signal, the mobile node 1 becomes aware that it is positioned within the cell managed by the first access point 21. The mobile node 1 accesses a wired network by way of the first access point 21, as it did previously.
In the communications denoted by 221, the mobile node 1 receives a beacon signal from the second access point 22. Based on the received beacon signal, the mobile node 1 becomes aware that the cell in which it is positioned has changed. Accordingly, the mobile node 1 conducts a handover due to the change of the cell (i.e., a handover in a link layer). That is, the mobile node 1 becomes aware that it is positioned in the cell managed by the second access point 22, and changes its link layer connection with the first access point 21 to a link layer connection with the second access point 22. The mobile node 1 accesses a wired network by way of the second access point 22 with which it forms a new connection.
In the communications denoted by 222, the mobile node 1 transmits information that its cell has changed to the first access router 31 via the second access point 22. The first access router 31 receives this information, not through other access routers, and becomes aware that the mobile node 1 is positioned within the subnet that it manages.
In the communications denoted by 223, the first access router 31 transmits information, which details that its subnet has not changed, to the mobile node 1 by way of the second access point 22. The mobile node 1 that received this information becomes aware that it is positioned in the subnet managed by the first access router 31. That is, the mobile node 1 becomes aware that it does not need to generate a new Internet protocol (IP) address for use in a new subnet. Accordingly, the mobile node 1 does not perform a handover due to the change of the subnet (i.e., a handover in the IP layer).
In the communications denoted by 224, the mobile node 1 receives a beacon signal from the second access point 22. Based on the received beacon signal, the mobile node 1 becomes aware that it is positioned within the cell managed by the second access point 22. The mobile node 1 connects to a wired network by way of the second access point 22, as it did previously.
In the communications denoted by 231, the mobile node 1 receives a beacon signal from the third access point 23. Based on the received beacon signal, the mobile node 1 becomes aware that its cell has changed. Accordingly, the mobile node 1 performs a handover due to the change of the cell (i.e., a handover in a link layer). That is, the mobile node 1 becomes aware that it is positioned within the cell managed by the third access point 23 and changes its link layer connection with the second access point 22 to a link layer connection with the third access point 23. The mobile node 1 accesses a wired network by way of the third access point 23 with which it forms a new connection.
In the communications denoted by 232, the mobile node 1 transmits information that its cell has changed to the first access router 31 by way of the third access point 23 and the second access router 32. The first access router 21 that has received this information by way of the second access router 32 becomes aware that the mobile node 1 has left its subnet.
In communications denoted by 233, the first access router 31 transmits to the mobile node 1 information that its subnet has changed, by way of the second access router 32 and the third access point 23. The mobile node 1 that has received this information becomes aware that the subnet in which it is positioned has changed. Accordingly, the mobile node 1 conducts a handover due to the change of the subnet (i.e., a handover in an Internet protocol (IP) layer). That is, the mobile node 1 becomes aware that it is positioned within the subnet managed by the second access router 32, and performs the communication operation denoted by 234.
In the communications denoted by 234, in order to generate a new IP address for use in the subnet managed by the second access router 32, the mobile node 1 requests the second access router 32 to provide a network prefix of the subnet managed by the access router 32, via the third access point 23. In response to the request, the mobile node 1 acquires the network prefix of the subnet managed by the second access router 32. Based on the network prefix, the mobile node 1 generates a new IP address and performs communications with the subnet managed by the second access router 32 using the new IP address.
In the communications denoted by 235, the mobile node 1 receives a beacon signal from the third access point 23. Based on the received beacon signal, the mobile node 1 becomes aware that it is positioned within the cell managed by the third access point 23. The mobile node 1 accesses a wired network by way of the third access point 23, as it did previously.
In the communications denoted by 241, the mobile node 1 receives a beacon signal from the fourth access point 24. Based on the received beacon signal, the mobile node 1 becomes aware that its cell has changed. Accordingly, the mobile node 1 performs a handover due to the change of the cell (i.e., a handover in the link layer). That is, the mobile node 1 becomes aware that it is positioned within the cell managed by the fourth access point 24 and changes its link layer connection with the third access point 23 to a link layer connection with the fourth access point 24. The mobile node 1 accesses a wired network by way of the fourth access point 24 with which it forms a new connection.
In communications denoted by 242, the mobile node 1 transmits information that its cell has changed to the second access router 32 via the fourth access point 24. The second access router 32 that received this information, not through another access router, becomes aware that the mobile node 1 is positioned within its subnet.
In the communications denoted by 243, the second access router 32 transmits information that its subnet has not changed to the mobile node 1 via the fourth access point 24. The mobile node 1 that received this information becomes aware that it is positioned within the subnet managed by the second access router 32. That is, the mobile node 1 becomes aware that it does not need to generate a new IP address for use in a new subnet. Accordingly, the mobile node 1 does not perform a handover due to the change of the subnet (i.e., a handover in the IP layer).
As described above, the mobile node 1, which checked for a change of a cell through a beacon signal received via an access point, communicates with an access router in order to check for a subnet change between a previous cell and a new cell. In this regard, the mobile node communicates with the access router in order to determine whether to perform only a link layer handover or both a link layer handover and an IP layer handover. Whenever the cell changes, mobile node has to communicate with the access router via an access point, and this can cause difficulty in realizing fast handovers.